One of my project: a led watch with 71 SMD LED. The microcontroller is a Microchips PIC16F728 running in 4MHz crystal oscillator and powered by CR2032 battery.
Circuit
The circuit is not that complicated, it only has 1 push button switch to adjust the time. This project main aim is to create a simple low cost LED wrist watch. That is the reason why I didn’t include any voltage regulators on the circuit to keep the cost as low as possible. There are NPN transistor is used to drive the LEDs. You might wonder why I didn’t used a PNP transistor on the positive side? Well, there is no need to do that since there is only 1 LED activated on each IO at a time. You can also opt to remove the transistor driver provided that you ensure that the current on each LED would not exceed 2mA.
Program
The program is coded with MikroC which has a free version with 2kB code size limit. Big enough for application like this. The clock timing is timer interrupt TM1 based. An interrupt is triggered every 500ms. Setting the timer interrupt is one of the most complicated task in microcontroller. Good thing that you can now easily do it by using a software from Mikroe, you can download it here. This software will make your task easy.
PCB
3d render of my PCB design
